Thousands call for help as storms lash Victoria

Severe thunderstorm warnings have been cancelled but wild weather continues to wreak havoc across large parts of Victoria as heavy rain pummels the state and forecasters say more chaos is yet to come.

The State Emergency Service (SES) has rescued 51 people and received about 3,000 calls for help after dozens of homes and businesses were flooded during super-cell storms last night.

Crews helped a woman and her two young children when their car became trapped in a flash flood at Mildura.

Firefighters have rescued a girl who was clinging to a tree branch after being swept away at Ashwood, in Melbourne's east.

And at Mulgrave, the fire brigade was called to assist a disabled man in a wheelchair who got stuck in water up to his hips.

SES spokesman Stephen Warren says large parts of the Melbourne area have been inundated.

"There's a lot of reports of water of significant depth on a lot of streets and highways, so around Melbourne at the moment there's certainly a lot of flooded waterways and there's a lot of homes that are flooded at the moment," he said.

Mr Warren says emergency workers have also found themselves in need.

"I've contacted a few staff and some volunteers tonight, just on a personal basis to see whether they were available to help out, and they've had significant rain and flooding through their own homes, so everyone's feeling the brunt of this rain storm," he said.

He is urging people not to go near floodwaters.

"The reason we don't want people out there in the water is you don't know what's out there around you and there is a possibility that things could change very rapidly around you and you could find yourself in difficulty very quickly," he said.

SES spokesman Lachlan Quick says the situation is set to worsen.

"Certainly across Mildura and other parts of north-western Victoria we've had significant flash flooding due to these thunderstorms," he said.

"We expect that situation to worsen before it improves. There will be significant rainfall occurring from midnight tonight [Friday] and that will go through until midnight tomorrow night [Saturday].

"So we are urging people in those areas to be alert to their conditions."

Residents from East Gippsland to the state's north-west have been warned of damaging winds, flash flooding and hail storms.

An emergency relief centre has been set up at the St Kilda town hall.

Large parts of the state have been drenched by more than 100 millimetres of rain.

Melbourne's south-eastern suburbs have been among the worst affected, as well as Mildura in the state's north-west, which has received record falls.

"Obviously up in the north-east ranges there's going to be a problem tonight [Friday], and into tomorrow morning [Saturday], so that's where we're looking for the heaviest rain to be, up to 150 millimetres in the north-east ranges and the alpine area," he said.

"Anywhere high east of Eildon towards the border, that whole area through there, potentially giving us 150 millimetres of rain."

He says the storms are rolling into areas that are already soaked.

"They appear to have been trailing over the one spot, so you get a series of thunderstorms over one area, giving you the classic flash flooding syndrome where there's no break between the storms, you just get one following another," he said.

"Hence you can get over 100 millimetres in some areas, particularly with the moisture we've got available."

Police sergeant Chris Parr says the water is receding in Mildura but the threat is not over.

"The water has slowly been going down and we've got a bit of a relief period at the moment, we've changed several officers over that have been working for 12 and 13 hours straight," he said.

"They've been able to go home because of the situation has calmed and the water is receding at the moment but we're worried about the next band that's coming through."

More than 134 mm has fallen at Lyndhurst, in Melbourne's outer south-east, and more than 100 mm has fallen at Mentone, Hampton Park and Moorabbin.

Several streets are still blocked because of the flash flooding.

A section of the Werribee Plaza has also been flooded, while the roofs at the Sanctuary Lakes shopping centre at Point Cook and the Shepparton police station have partially collapsed.

Bendigo incident controller Wayne Grinsize says crews are worried about a dam wall giving way near Junortoun in central Victoria.

"There are two dams, one above the other. We've got some concerns for the wall on the top dam," he said.

"In saying that, they're not huge dams, around about 2,000-meg, the top dam is, that's seeping some water out of the dam wall at the moment, so we're just door-knocking about 40 to 50 houses below that dam wall just to warn those people."